Hydrocarbon production starts with mining. Either surface mining with large cranes and trucks used for oil sands mining or drilling a well to mine the hydrocarbons in a subsurface formation. In either case, byproducts from mining, drilling, completing and/or producing hydrocarbons range from drill cuttings to frack flowback water to produced water and huge volumes of tailings in the case of oil sands surface mining (collectively referred to as “mining byproducts”).
Solvents and/or valuable drilling fluids (collectively referred to as “mining fluids”) are used in the mining or drilling process to, among other things, provide hydrostatic pressure, cool and clean the drill bit, carry out drill cuttings (e.g., rock, soil, sand, etc.), and suspend the drill cuttings when the drill is not active. The cost of most drilling fluids is directly proportional to the cost of crude oil. Hence, oil based muds (“OBM”) are predominantly diesel, and synthetic based muds (“SBM”) are synthetic oils similar to Shell Rotella®. For example, formate drilling fluids manufactured by Cabot Corporation are extremely expensive but are environmentally safe, do not contain solids and can be used within high temperature and high pressure formations. Likewise, synthetic based drilling fluids are commonly employed for offshore drilling because the drill cuttings can be discharged overboard as long as the Fluid Retention On Cuttings (“ROC”) is less than what is required by regulations.
The mixture of mining fluids and mining byproducts that exit the mine or well also contain hydrocarbons. This mixture is typically processed by a solids control system (e.g., shale shakers, mud gas separators, desanders, desilters, degassers, cleaners, etc.) to substantially separate the mining fluids and hydrocarbons from the mining byproducts. But these solids control systems do not remove all of the mining fluids and hydrocarbons from the mining byproducts. As a result, these valuable mining fluids and hydrocarbons may end up in a tailings pond, the bottom of the ocean or shipped to a Treatment, Recovery and Disposal (“TRD”) facility.
Vertical Centrifuges are commonly employed offshore for reducing the ROC to below discharge limits. However, Loss Circulation Material (“LCM”) and cement cannot be effectively treated in a vertical centrifuge. It clogs the centrifuge and it must be shut down and cleaned, thus it is usually bypassed during cementing operations or when a LCM Pill is used to prevent losing circulation and fluids into the formation. Another treatment system uses thermal desorption units, which are are bulky and have many moving parts. Likewise, thermal desorption units typically employ indirect heating, which is inefficient when compared to direct heating.
Air dryers and friction dryers, such as Schlumberger's (M-I Swaco) Hammermill are commonly employed, but neither have been successful at recovering base fluids. Why? Both dryer types comminute the cuttings into very fine powders which makes it difficult to separate the base fluid from the fine cuttings. Likewise, air dryers can produce an explosive mixture since drilling fluids contain fuels (diesel, synthetic oil, etc). Although Schlumberger markets a Zero Discharge thermal desorption TPS system, the system still only achieves a removal of Total Percent Hydrocarbons (TPH) of less than 0.5%. Finally, the U.S. Department Of Energy's Drilling Waste Management Information System discloses many different thermal technologies for treating drilling waste.
When the price of crude oil was low, a ROC near the limits was not perceived as a problem. However, with new regulations pushing lower ROC limits in addition to high crude oil prices, recovering mining fluids from the mining byproducts has become a priority and is now an environmentally sustainable goal for many oil and gas companies. Moreover, the cost of some mining fluids, such as formate drilling fluids containing Cesium, makes recovering these mining fluids from the mining byproducts very desirable both ecomonically and ecologically.
Therefore, a need exists for a plasma arc torch that can be operated in multiple modes.